In the field of clinical and molecular chemistry, analyses are often automated using in clinical diagnostic analyzer systems like clinical chemistry analyzer systems and molecular clinical diagnostic analyzer systems. For these systems, it is necessary to measure very small liquid volumes in the microliter and even in the nanoliter range with sufficient accuracy, e.g. for calibrating automatic pipetting devices which are integral parts of analyzer systems of the above mentioned kinds. For this purpose a gravimetric volume determination is a preferred method. Conventional methods of this kind require a lot of manual handling and are therefore time consuming. This is so, in particular because the various apparatuses needed for performing gravimetric volume determination are not part of an automated clinical diagnostic analyzer system. For instance, in the case of a conventional gravimetric volume determination, each liquid volume to be weighed is manually pipetted into a weighing container of a special weighing instrument, and the control of the procedure and evaluation of results for the gravimetric volume determination are carried out by a computer connected with the weighing instrument. To convert the weighing result to the volume to be determined, the ambient temperature, air pressure and humidity data must be manually entered into the computer before performing a calibration of an automatic pipetting device of an analyzer system. The ambient temperature, air pressure and humidity data may vary over a relatively wide range, depending on the specific environmental conditions at the place where the analyzer system is located. Moreover, since the location and environment of the analyzer system may be changed from time to time, it cannot be assumed that the temperature, air pressure and humidity data have stable values.
A further drawback of conventional means for performing gravimetric volume determinations is that the required additional apparatuses must be located near the analyzer apparatus and therefore increase the size of the space required for operation of the analyzer. Moreover, the size of additional conventional apparatuses required for performing gravimetric volume determinations is such that they cannot be located within the analyzer apparatus.
Moreover, quality control in the manufacture of clinical diagnostic analyzer systems and field tests of such systems require a large number of gravimetric volume determinations for the above mentioned calibration purposes. In addition, periodic calibrations of automatic pipetting devices have to be performed by gravimetric volume determinations for analyzer systems which are already installed and in operation.